Implant formulations can be designed to release bioactive agents into a fluid or tissue of a subject. Useful formulations are those that comprise a polymer that releases the bioactive agent as the polymer biodegrades. One purpose of the polymer is to restrict the influx of water, which in turns controls the dissolution of the bioactive agent followed by the release of the bioactive agent from the implant. While the polymer provides a number of advantages, such as restricting water influx, it can be difficult to provide an appropriate polymer formulation that is effective to achieve a targeted or effective release profile. A variety of different release profiles are needed in the pharmaceutical arts that generally depend on variables in the subject to be treated and the particular characteristics of the disorder. Unfortunately, a typical drug-delivery strategy based on a single implant composition often fails to meet the needs of varying release profiles.
As such, a need exists for drug-delivery strategies that can effectively provide for a desired release profile without undue manufacturing limitations. These needs and other needs are satisfied by the present invention.